Based on food combining principle some days you eat only vegetables, other only fruits and on some starch carbonates are allowed. Meat and other protein are not allowed until day 19. It is ridiculously low on daily calorie intake and is usually around 800 calorie for the day. The diet is really strict and picky, meaning, if you miss the time period for a particular food, you can't eat that food again until tomorrow. Basically, you are starving yourself, which only works until you decide to actually eat again. Then all of the weight comes back. Most of the weight loss is water weight and weight loss due to laxative effect of eating so much fruit.
For more details, check out: http://www.diet.com/store/facts/beverly-hills-diet